Can I drive someone else's car under my car insurance?
The 'Drive other cars' extension is not available on every policy, so you'll need to check your documents to see if it's included on yours. If it's included, it will be shown under section 3 of your Certificate of Motor Insurance. (How can I access my policy documents?)
The extension allows the policyholder to drive someone else's car with the owner's permission. However, cover for this car is limited to third party damage only and is not comprehensive. This means there's no cover for damage to or theft of the borrowed car itself. The 'Drive other cars' extension does not apply to named drivers.